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30ma C4 grasses arose during low Atmos. CO2

[my interp. C4 grasses succeeded over C3 plants because the excess CO2 in Earth s atmosphere had been converted into sugars/starches/cellulose by

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, Dec 21, 2007

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[my interp. C4 grasses succeeded over C3 plants because the excess CO2
in Earth's atmosphere had been converted into
sugars/starches/cellulose by algae/mosses/gymnosperms/angiosperms and
buried under water during high sea levels (today's oil/coal/methane),
resulting in proportionately high O2 levels. C4 plants are less
efficient photosynthsizers but faster growing, so were selected in
areas where C3 plants were marginal:
lightning/fire plains with dry seasons (wind pollinated grasses),
non-acidic swamps/marshes with varying O2 and NaCl (reeds),
forest openings (bamboo)
======

HEALTH NEWS
Greenhouse gases linked to evolution of C4 grasses

By ANI
Friday December 21, 01:39 PM

Washington, Dec 21 (ANI): A new study has linked greenhouse gases to
the evolution of a specific group of plants, termed C4 grasses, such
as corn, sugarcane, sorghum, and millets.

In the study, evolutionary biologists provided strong evidence that
changes in global carbon dioxide levels probably had a significant
influence on the emergence of C4 grasses, which includes major cereal
crops, plants used for biofuels, and species that represent important
components of grasslands across the world.

These plants are specially equipped to combat an energetically costly
process, known as photorespiration, that can occur under conditions of
high temperature, drought, high salinity, and-with relevance to these
latest findings-low carbon dioxide levels.

Although a combination of any of these factors might have provided the
impetus behind the evolution of the various C4 lineages, it had been
widely speculated that a drop in global carbon dioxide levels,
occurring approximately 30 million years ago during the Oligocene
period, might have been the major driving force.

However, establishing the link between the two has proven difficult
partly because there are no known fossils of C4 plants from this period.

Pascal-Antoine Christin and colleagues from the University of
Lausanne, Switzerland decided to take an alternative approach to date
a large group of grasses.

By using a 'molecular clock' technique, the researchers were able to
determine that the Chloridoideae subfamily of grasses emerged
approximately 30 million years ago, right around the time global
carbon dioxide levels were dropping. Furthermore, a model of the
evolution of these grasses suggests that this correlation is not a
trivial coincidence and instead reflects a causal relationship.

Researchers noted in their study, many of the C4 grasses evolved after
the drop in global carbon dioxide levels 30 million years ago. The
authors speculate that while an atmosphere low in carbon dioxide
established the basic conditions necessary for C4 evolution, other
ecological factors might be at work.

In light of this, the researchers hope to apply the same approaches
used in the study described here to investigate the role of other
variables, such as drought, salinity, and flooding, in the evolution
of C4 plants. In addition to improving the understanding of how
climate changes influenced ecosystems in the past, such studies may
allow predictions of how human activities could affect the planet in
the future.

Indeed, with regard to global carbon dioxide levels, researchers said:
"Besides its influence on climatic variables, increased CO2
concentration could trigger important ecological changes in major
terrestrial ecosystems by affecting the distribution of C4-dominated
biomes and the affiliated flora and fauna."

This implies that a reversal of the conditions that favoured C4 plants
could potentially lead to their demise, a startling prospect if one
considers the human race's reliance on C4 crops.

The study is published online on December 20th in the journal Current
Biology. (ANI)

--- In AAT@yahoogroups.com, "DDeden" <alas_my_loves@...> wrote:
>
> [my interp. C4 grasses succeeded over C3 plants because the excess CO2
> in Earth's atmosphere had been converted into
> sugars/starches/cellulose by algae/mosses/gymnosperms/angiosperms and
> buried under water during high sea levels (today's oil/coal/methane),
> resulting in proportionately high O2 levels. C4 plants are less
> efficient photosynthsizers but faster growing, so were selected in
> areas where C3 plants were marginal:
> lightning/fire plains with dry seasons (wind pollinated grasses),
> non-acidic swamps/marshes with varying O2 and NaCl (reeds),
> forest openings (bamboo)
> ======
>
> HEALTH NEWS
> Greenhouse gases linked to evolution of C4 grasses
>
> By ANI
> Friday December 21, 01:39 PM
>
> Washington, Dec 21 (ANI): A new study has linked greenhouse gases to
> the evolution of a specific group of plants, termed C4 grasses, such
> as corn, sugarcane, sorghum, and millets.
>
> In the study, evolutionary biologists provided strong evidence that
> changes in global carbon dioxide levels probably had a significant
> influence on the emergence of C4 grasses, which includes major cereal
> crops, plants used for biofuels, and species that represent important
> components of grasslands across the world.
>
> These plants are specially equipped to combat an energetically costly
> process, known as photorespiration, that can occur under conditions of
> high temperature, drought, high salinity, and-with relevance to these
> latest findings-low carbon dioxide levels.
>
> Although a combination of any of these factors might have provided the
> impetus behind the evolution of the various C4 lineages, it had been
> widely speculated that a drop in global carbon dioxide levels,
> occurring approximately 30 million years ago during the Oligocene
> period, might have been the major driving force.
>
> However, establishing the link between the two has proven difficult
> partly because there are no known fossils of C4 plants from this period.
>
> Pascal-Antoine Christin and colleagues from the University of
> Lausanne, Switzerland decided to take an alternative approach to date
> a large group of grasses.
>
> By using a 'molecular clock' technique, the researchers were able to
> determine that the Chloridoideae subfamily of grasses emerged
> approximately 30 million years ago, right around the time global
> carbon dioxide levels were dropping. Furthermore, a model of the
> evolution of these grasses suggests that this correlation is not a
> trivial coincidence and instead reflects a causal relationship.
>
> Researchers noted in their study, many of the C4 grasses evolved after
> the drop in global carbon dioxide levels 30 million years ago. The
> authors speculate that while an atmosphere low in carbon dioxide
> established the basic conditions necessary for C4 evolution, other
> ecological factors might be at work.
>
> In light of this, the researchers hope to apply the same approaches
> used in the study described here to investigate the role of other
> variables, such as drought, salinity, and flooding, in the evolution
> of C4 plants. In addition to improving the understanding of how
> climate changes influenced ecosystems in the past, such studies may
> allow predictions of how human activities could affect the planet in
> the future.
>
> Indeed, with regard to global carbon dioxide levels, researchers said:
> "Besides its influence on climatic variables, increased CO2
> concentration could trigger important ecological changes in major
> terrestrial ecosystems by affecting the distribution of C4-dominated
> biomes and the affiliated flora and fauna."
>
> This implies that a reversal of the conditions that favoured C4 plants
> could potentially lead to their demise, a startling prospect if one
> considers the human race's reliance on C4 crops.
>
> The study is published online on December 20th in the journal Current
> Biology. (ANI)
>

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